If the scraping is done properly, it is not worth Google's trouble to find you. Our source code separates the "fetch" portion of program, which is done by curl or wget, from the searcher interface and parsing of the fetched results. If the fetching is done by a server on a different Class C address from the website that shows the scraped results, there is little that Google can do to find the IP address that is responsible for the actual fetch.

and Chris states:

Conveniently forgetting that his hack of an application forgets to change the useragent of the request from the curl/wget defaults. Thereby leaving the fetch machines' ip addresses sitting ducks in those query logs that Brandt believes last an eternity.

Cooperative Ad Network to Adopt NoFollow Tag?
members at the Digital Point forums think not...two quotes sum it up:
"would that not defeat the object of having the links if the search engines ignored them?"
and
"Exactly, who'd actually use the Co-Op for anything other than IBLs?"